This proposal addresses fundamental issues in the evolution of biological knowledge and reasoning, across cultures and across development. Researchers have long recognized that children are not tabulae rosae. Instead, they bring with them theories and concepts of the world. When these differ radically from those of adults, children's existing theories can be obstacles to learning. Years of research have suggested that the very concepts that adults hold as central (e.g., alive, animal), may be represented in an altogether different fashion in children. Unfortunately, this prior research has focused almost exclusively on middle-class, urban, technologically-advanced populations. This narrow empirical base makes it impossible to determine a) whether the theories held by these children are universal, b) how these early theories are shaped by culture and input conditions, c) how to best characterize the mechanisms underlying developmental change. The goal of this proposal is to redress this limitation by identifying core biological concepts and reasoning in young children from different cultural groups and to trace their developmental trajectories into adulthood. Populations include Chicago (suburban; urban), Wisconsin (rural majority culture; rural native American (Menominee); Mexico (Yukatek Maya; Ladino). dramatically expands the database on concept development and provides new understanding of normative theories by analyzing the various developmental motivations and patterns. Each population participates in 4 series of experiments, each aimed at a different aspect of knowledge within the biological domain. Experimental tasks include: (1) name generation, (2) reasoning tasks, (3) parent-child speech dyads, and (4) ethnographic description of classroom and other instructional content. These developmental, cross-cultural experiments will help us ascertain which biological concepts (if any) are universal, and determine how these are shaped by the culture in which an individual is immersed. Ensuing knowledge of particular cultural conceptions about the biological world and how it works may be critical in understanding the educational possibilities for learning about biology - the new cornerstone of any science curriculum in the twenty-first century - and for maintaining environmental health.